Apparatus and method for diagnosing faults in a fieldbus interface module

ABSTRACT

A method and system for detecting faults in a communication interface is disclosed. The communication interface is connected to a field device and a device bus comprising generating periodic diagnostic pulse by a programing unit. The programming unit is communicatively connected to the controller and a controller interface and provides the diagnostic pulse to a multiplexer to periodically apply the diagnostic pulses from the programming unit to a first winding of a transformer. The programming unit provides the diagnostic pulse to the isolation unit. A sensing unit senses a voltage drop across a sense resistor, the sensing unit having an input connected to the sense resistor and an output connected to the programming unit. The sensing unit communicates a sense signal based on the comparison to the programming unit, and switches from a primary or a secondary module to the other based on the sense signal.

FIELD

The present disclosure relates generally to industrial process controland automation systems. More specifically, this disclosure relates tothe diagnosis of faults in the fieldbus interface module of a processcontrol system.

BACKGROUND

In an industrial process control system, an interface module isincorporated to communicate between the control system and plurality offield devices. Interface modules communicate in different protocols.Different protocols are suitable for different purposes. Protocols arewidely used for industrial process control and automation, such as tointerconnect sensors, actuators, and input/output (I/O) of controllersin an industrial facility. Different protocol systems are often deployedas digital I/O networks for proprietary controllers. This protocolenables two-way communication between filed devices and the controlsystem. One such protocol used for communication in an industrialcontrol system is Foundation Fieldbus. Interface modules used in theFoundation Fieldbus protocol are generally known as fieldbus interfacemodules (FIM). The FIM integrates the Foundation Fieldbus to the fielddevices connected with a control system. In some instances, theseinterface modules can become faulty and fail to communicate in thedesired manner. There may be various reasons for faults originating atthe FIM including faulty internal hardware or external factors such asconnectors, cables or terminations. Loss of control of field devices isan important concern in a Foundation Fieldbus system design. Animportant area where loss of control occurs is in the redundancyfunction of a FIM.

FIMs are typically implemented in redundant pairs. In redundant pairconfiguration, one of the FIM performs the functions as a primary FIMand the other functions as the secondary. In this redundancyconfiguration, the primary and the secondary FIM work in sync. Theprimary FIM is responsible to communicate the instructions from thecontrol system to the field devices. The secondary FIM is disposed totake charge of the communication in the field link between the controlsystem and the field devices if the primary FIM fails. Accordingly, itbecomes imperative to ascertain any potential fault in a FIM in order totrigger the changeover to its redundant partner. However, in existingFIMs, it is difficult to differentiate between hardware failures in theFIM from failures induces by noise on the field link. Thus, it becomesdifficult to ascertain the actual origin of the fault.

Therefore, there arises a need for diagnostics, that can be embedded inthe FIM, to determine a FIM hardware fault. This fault detection wouldensure seamless and reliable communications between the FIM and thefield devices.

SUMMARY

In accordance with an embodiment, the present disclosure relates to anapparatus for detecting faults in a fieldbus interface module. Thefieldbus interface module is connected to a field device and a devicebus. The interface module comprises, a controller configured to generatea device bus communication signal TXE, and a programming unitcommunicatively connected to the controller and a controller interface.The programming unit is configured to detect faults in the fieldbusinterface module and generate periodic diagnostic pulses. A transformerhas a first winding connected to the controller interface and a secondwinding connected to the device bus. A multiplexer is connected to theprogramming unit and configured to periodically apply the diagnosticpulses from the programming unit to the first winding of thetransformer. An isolation unit is also connected to the programming unitthat is configured to periodically apply the diagnostic pulses from theprogramming unit to the transformer's second winding. A sense resistoris connected in series between the first winding of the transformer anda sensing unit. The sensing unit connects to the programming unit and isarranged to determine the voltage across the sense resistor whereby thesensed voltage is communicated to the programming unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will hereinafter be described in conjunctionwith the Figures, wherein like numerals denote like elements.

FIG. 1 illustrates an example industrial process control and automationsystem according to this disclosure.

FIG. 2 illustrates an Input Output Terminal Assembly in communicationwith a control system and field devices.

FIG. 3 illustrates a block diagram indicating the components of FIMwhich take part in the FF (Foundation Fieldbus) communication.

FIG. 4 describes a method according to this disclosure.

Skilled artisans will appreciate that elements in FIGS. 1-4 areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inFIG. 1 may be exaggerated relative to other elements to help to improveunderstanding of various embodiments of the present disclosure. Also,common but well-understood elements that are useful or necessary in acommercially feasible embodiment may not be depicted in order tofacilitate a less obstructed view of these various embodiments of thepresent disclosure.

DETAILED DESCRIPTION

Various embodiments herein relate to fault detection in interfacemodules. FIGS. 1 through 4, discussed below, and the various embodimentsused to describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the invention. Those skilled in the artwill understand that the principles of the invention may be implementedin any type of suitably arranged device or system.

FIG. 1 illustrates an industrial process control and automation system100 according to an embodiment of the present disclosure. As shown inFIG. 1, the system 100 includes various components that facilitateproduction or processing of at least one product or other material. Forinstance, the system 100 is used here to facilitate control overcomponents in one or multiple plants 101 a-101 n. Each plant 101 a-101 nrepresents one or more processing facilities (or one or more portionsthereof), such as one or more manufacturing facilities for producing atleast one product or other material. In general, each plant 101 a-101 nmay implement one or more processes and can individually or collectivelybe referred to as a process system. A process system generallyrepresents any system or portion thereof configured to process one ormore products or other materials in some manner.

In FIG. 1, the system 100 is implemented using the Purdue model ofprocess control. In the Purdue model, “Level 0” may include one or moresensors 102 a and one or more actuators 102 b. The sensors 102 a andactuators 102 b represent components in a process system that mayperform any of a wide variety of functions. For example, the sensors 102a could measure a wide variety of characteristics in the process system,such as temperature, pressure, or flow rate. Also, the actuators 102 bcould alter a wide variety of characteristics in the process system. Thesensors 102 a and actuators 102 b could represent any other oradditional components in any suitable process system. Each of thesensors 102 a includes any suitable structure for measuring one or morecharacteristics in a process system. Each of the actuators 102 bincludes any suitable structure for operating on or affecting one ormore conditions in a process system.

At least one network 104 is coupled to the sensors 102 a and actuators102 b. The network 104 facilitates interaction with the sensors 102 aand actuators 102 b. For example, the network 104 could transportmeasurement data from the sensors 102 a and provide control signals tothe actuators 102 b. The network 104 could represent any suitablenetwork or combination of networks. As a particular example, the network104 could represent a FOUNDATION FIELDBUS H1 network.

In the Purdue model, “Level 1” may include one or more controllers 106,which are coupled to the network 104. Among other things, eachcontroller 106 may use the measurements from one or more sensors 102 ato control the operation of one or more actuators 102 b. For example, acontroller 106 could receive measurement data from one or more sensors102 a and use the measurement data to generate control signals for oneor more actuators 102 b. Each controller 106 includes any suitablestructure for interacting with one or more sensors 102 a and controllingone or more actuators 102 b. Each controller 106 could, for example,represent a proportional-integral-derivative (PID) controller or amultivariable controller, such as a Robust Multivariable PredictiveControl Technology (RMPCT) controller or other type of controllerimplementing model predictive control (MPC) or other advanced predictivecontrol (APC). As a particular example, each controller 106 couldrepresent a computing device running a real-time operating system.

Two networks 108 are coupled to the controllers 106. The networks 108facilitate interaction with the controllers 106, such as by transportingdata to and from the controllers 106. The networks 108 could representany suitable networks or combination of networks. As a particularexample, the networks 108 could represent a redundant pair of Ethernetnetworks, such as a FAULT TOLERANT ETHERNET (FTE) network from HONEYWELLINTERNATIONAL INC.

At least one switch/firewall 110 couples the networks 108 to twonetworks 112. The switch/firewall 110 may transport traffic from onenetwork to another. The switch/firewall 110 may also block traffic onone network from reaching another network. The switch/firewall 110includes any suitable structure for providing communication betweennetworks, such as a HONEYWELL CONTROL FIREWALL (CF9) device. Thenetworks 112 could represent any suitable networks, such as an FTEnetwork.

In the Purdue model, “Level 2” may include one or more machine-levelcontrollers 114 coupled to the networks 112. The machine-levelcontrollers 114 perform various functions to support the operation andcontrol of the controllers 106, sensors 102 a, and actuators 102 b,which could be associated with a particular piece of industrialequipment (such as a boiler or other machine). For example, themachine-level controllers 114 could log information collected orgenerated by the controllers 106, such as measurement data from thesensors 102 a or control signals for the actuators 102 b. Themachine-level controllers 114 could also execute applications thatcontrol the operation of the controllers 106, thereby controlling theoperation of the actuators 102 b. In addition, the machine-levelcontrollers 114 could provide secure access to the controllers 106. Eachof the machine-level controllers 114 includes any suitable structure forproviding access to, control of, or operations related to a machine orother individual piece of equipment. Each of the machine-levelcontrollers 114 could, for example, represent a server computing devicerunning a MICROSOFT WINDOWS operating system. Although not shown,different machine-level controllers 114 could be used to controldifferent pieces of equipment in a process system (where each piece ofequipment is associated with one or more controllers 106, sensors 102 a,and actuators 102 b).

One or more operator stations 116 are coupled to the networks 112. Theoperator stations 116 represent computing or communication devicesproviding user access to the machine-level controllers 114, which couldthen provide user access to the controllers 106 (and possibly thesensors 102 a and actuators 102 b). As particular examples, the operatorstations 116 could allow users to review the operational history of thesensors 102 a and actuators 102 b using information collected by thecontrollers 106 and/or the machine-level controllers 114. The operatorstations 116 could also allow the users to adjust the operation of thesensors 102 a, actuators 102 b, controllers 106, or machine-levelcontrollers 114. In addition, the operator stations 116 could receiveand display warnings, alerts, or other messages or displays generated bythe controllers 106 or the machine-level controllers 114. Each of theoperator stations 116 includes any suitable structure for supportinguser access and control of one or more components in the system 100.Each of the operator stations 116 could, for example, represent acomputing device running a MICROSOFT WINDOWS operating system.

At least one router/firewall 118 couples the networks 112 to twonetworks 120. The router/firewall 118 includes any suitable structurefor providing communication between networks, such as a secure router orcombination router/firewall. The networks 120 could represent anysuitable networks, such as an FTE network.

In the Purdue model, “Level 3” may include one or more unit-levelcontrollers 122 coupled to the networks 120. Each unit-level controller122 is typically associated with a unit in a process system, whichrepresents a collection of different machines operating together toimplement at least part of a process. The unit-level controllers 122perform various functions to support the operation and control ofcomponents in the lower levels. For example, the unit-level controllers122 could log information collected or generated by the components inthe lower levels, execute applications that control the components inthe lower levels, and provide secure access to the components in thelower levels. Each of the unit-level controllers 122 includes anysuitable structure for providing access to, control of, or operationsrelated to one or more machines or other pieces of equipment in aprocess unit. Each of the unit-level controllers 122 could, for example,represent a server computing device running a MICROSOFT WINDOWSoperating system. Although not shown, different unit-level controllers122 could be used to control different units in a process system (whereeach unit is associated with one or more machine-level controllers 114,controllers 106, sensors 102 a, and actuators 102 b).

Access to the unit-level controllers 122 may be provided by one or moreoperator stations 124. Each of the operator stations 124 includes anysuitable structure for supporting user access and control of one or morecomponents in the system 100. Each of the operator stations 124 could,for example, represent a computing device running a MICROSOFT WINDOWSoperating system.

At least one router/firewall 126 couples the networks 120 to twonetworks 128. The router/firewall 126 includes any suitable structurefor providing communication between networks, such as a secure router orcombination router/firewall. The networks 128 could represent anysuitable networks, such as an FTE network.

In the Purdue model, “Level 4” may include one or more plant-levelcontrollers 130 coupled to the networks 128. Each plant-level controller130 is typically associated with one of the plants 101 a-101 n, whichmay include one or more process units that implement the same, similar,or different processes. The plant-level controllers 130 perform variousfunctions to support the operation and control of components in thelower levels. As particular examples, the plant-level controller 130could execute one or more manufacturing execution system (MES)applications, scheduling applications, or other or additional plant orprocess control applications. Each of the plant-level controllers 130includes any suitable structure for providing access to, control of, oroperations related to one or more process units in a process plant. Eachof the plant-level controllers 130 could, for example, represent aserver computing device running a MICROSOFT WINDOWS operating system.

Access to the plant-level controllers 130 may be provided by one or moreoperator stations 132. Each of the operator stations 132 includes anysuitable structure for supporting user access and control of one or morecomponents in the system 100. Each of the operator stations 132 could,for example, represent a computing device running a MICROSOFT WINDOWSoperating system.

At least one router/firewall 134 couples the networks 128 to one or morenetworks 136. The router/firewall 134 includes any suitable structurefor providing communication between networks, such as a secure router orcombination router/firewall. The network 136 could represent anysuitable network, such as an enterprise-wide Ethernet or other networkor all or a portion of a larger network (such as the Internet).

In the Purdue model, “Level 5” may include one or more enterprise-levelcontrollers 138 coupled to the network 136. Each enterprise-levelcontroller 138 is typically able to perform planning operations formultiple plants 101 a-101 n and to control various aspects of the plants101 a-101 n. The enterprise-level controllers 138 can also performvarious functions to support the operation and control of components inthe plants 101 a-101 n. As particular examples, the enterprise-levelcontroller 138 could execute one or more order processing applications,enterprise resource planning (ERP) applications, advanced planning andscheduling (APS) applications, or any other or additional enterprisecontrol applications. Each of the enterprise-level controllers 138includes any suitable structure for providing access to, control of, oroperations related to the control of one or more plants. Each of theenterprise-level controllers 138 could, for example, represent a servercomputing device running a MICROSOFT WINDOWS operating system. In thisdocument, the term “enterprise” refers to an organization having one ormore plants or other processing facilities to be managed. Note that if asingle plant 101 a is to be managed, the functionality of theenterprise-level controller 138 could be incorporated into theplant-level controller 130.

Various plant applications 140 could also be executed in the system 100.In this example, the plant applications 140 are shown as residing onLevel 5 of the system 100, although plant applications 140 could resideon other or additional levels of the system 100. The plant applications140 could represent any suitable applications that are executed byserver computers or other computing devices.

Access to the enterprise-level controllers 138 and plant applications140 may be provided by one or more enterprise desktops (also referred toas operator stations) 142. Each of the enterprise desktops 142 includesany suitable structure for supporting user access and control of one ormore components in the system 100. Each of the enterprise desktops 142could, for example, represent a computing device running a MICROSOFTWINDOWS operating system.

Various levels of the Purdue model can include other components, such asone or more databases. The database(s) associated with each level couldstore any suitable information associated with that level or one or moreother levels of the system 100. For example, a historian 144 can becoupled to the network 136. The historian 144 could represent acomponent that stores various information about the system 100. Thehistorian 144 could, for instance, store information used duringproduction scheduling and optimization. The historian 144 represents anysuitable structure for storing and facilitating retrieval ofinformation. Although shown as a single centralized component coupled tothe network 136, the historian 144 could be located elsewhere in thesystem 100, or multiple historians could be distributed in differentlocations in the system 100.

In particular embodiments, the various controllers and operator stationsin FIG. 1 may represent computing devices. For example, each of thecontrollers 106, 114, 122, 130, 138 and each of the operator stations116, 124, 132, 142 could include one or more processing devices and oneor more memories for storing instructions and data used, generated, orcollected by the processing device(s). Each of the controllers 106, 114,122, 130, 138 and each of the operator stations 116, 124, 132, 142 couldalso include at least one network interface, such as one or moreEthernet interfaces or wireless transceivers, facilitating communicationover one or more networks or communication paths.

Various types of technologies are available for linking field devicessuch as sensors, actuators, and controllers etc. with the field bus. Onesuch type of technology is the foundation field bus network, which isused to interconnect sensors, actuators, and input/output (I/O) of thecontrollers in an industrial facility.

FIG. 2 illustrates field bus interface modules (FIMs) integrated in aninput output terminal assembly (IOTA) and implemented as a redundantpair. The IOTA 202 is connected to a plurality of field devices 203 nand a control system 201 as illustrated in FIG. 2. The IOTA 202 includestwo independent FIMs, a primary FIM 2021 and a secondary FIM 2022. In atypical configuration, the two FIMs are installed on the IOTA in aredundant configuration, one of the two FIMs functions as primaryinterface to the field devices 203 n and the other functions as asecondary interface. The control system 201 is communicatively connectedto IOTA 202 and can preferably be an Automation System Server. Thecommunicative connection between the server 201 and IOTA 202 may be viaan ethernet link using a Common Data Access (CDA) protocol.

The plurality of field devices 203 n connected to the FIM, includesensors, actuators, valves and can include all technical equipment orhardware used for exercising control in an industrial control andautomation system. The IOTA functions as a bridge and communicatescommands and instructions from the control system 201 to the fielddevices 203 n.

The two FIMs 2021 and 2022, operate as a redundant pair. Any one of thetwo FIMs 2021 and 2022 can function as a primary FIM. The primary FIM(in this case 2021) communicates information from Foundation Fieldbus(FF) devices to the server 201 via the CDA protocol. Both FIMs cancommunicate to the fieldbus devices over a FF communication links. Anyone of the FIM may function as the primary FIM when it receivescommunication from the control system, instructing it to initializefunctions as the primary FIM. This communication may come from anyhigher-order control system or the operator. The secondary FIM 2022remains on the bus in standby mode and maintains a configuration filethat is continuously synchronized with the primary FIM's configurationfile. Thus, if the primary FIM 2021 surrenders control, fails, or mustbe taken offline, the secondary FIM can immediately assume the primarycommunication link between the FF devices and the control system.

The primary FIM 2021 is in-charge of communication until a failureoccurs, in case of any failure, or a switchover is initiated by thecontrol system. An important area where loss of control occurs is at theFIM redundancy switchover. At the time of fault in a primary FIM, theprimary FIM 2021 continues to communicate with the server even thoughsecondary FIM 2022 takes over for the field devices. Conventionally,there is a lack of complete control over switching, between a primaryFIM 2021 and a secondary FIM 2022. This lack of control over switchingmay result in abnormal behavior of industrial field devices, affectingthe entire industrial process.

If there is a fault in the hardware of the primary FIM 2021, the PrimaryFIM 2021 continues to communicate with the Experion Server via CDAcommunication even though secondary FIM 2022 takes over as a link activescheduler (LAS) for the FF devices 203 n. This results in live listmismatch and loss of view for the devices connected to the foundationfieldbus (FF) communication links of the FIMs.

FIG. 3 illustrates the apparatus 300 of the present invention, thatprovides hardware diagnostics to a FIM to determine hardware faults inan included transformer of the FIM. A control system 301 is connected toa FIM 2021 over an ethernet connection. Although for exemplary functionthis figure illustrates the FIM 2021, however the same structuralcomponents and hardware are present in FIM 2022. The control system 301performs the communication that provides control over a plurality ofindustrial equipment and field devices 312 n used in the automationsystem by providing them with specific commands. The FIM 2021 forms aninterface between the control system 301 and the field devices 312 n.The FIM 2021 is comprised of an ethernet physical layer, amicroprocessor 302, a FF controller 304, a media attachment unit MAU 305and a transformer 308 among other hardware elements. The microprocessor302 serves as the gateway for communication between the FIM 2021 and thecontrol system 301.

The microprocessor 302 is connected to the control system by theethernet physical layer. The microprocessor 302 uses an ethernet basedstack to communicate with the control system 301 via the ethernetphysical layer and a fieldbus stack to communicate with the FFcontroller 304. The FF controller 304 generates the commands andinstructions, required to communicate with the respective field devices312 n. The FF controller 304 receives control data from themicroprocessor 301 and generates the desired commands and instructionfor the field devices 312 n. The output of the FF controller 304 iscommunicated to the MAU 305. The MAU 305 is implemented as a discretecircuit which performs voltage mode diagnostics and related activitieswith respect to the signals generated or sent by the FF controller 304.The MAU 305 is connected to transformer 308. The transformer 308 in theFIM 2021, provides link isolation to field devices 312 n from thecontrol system 301. There may be several reasons that may cause the FIM2021 to run into a fault condition, including faults within the hardwareof the FIM 2021 and faults external to the FIM 2021. For example, anexternal fault could be termination or catastrophic severing of the linkand its connections. Fault conditions within the FIM 2021 can comprisefailures in the ethernet physical layer, microprocessor 301, FFcontroller 304 and the MAU 305. These types of internal failures can beascertained through use of diagnostic firmware run by the FF controller304. However, there does not exist any technique or mechanism known to aperson skilled in the art, to ascertain a fault in the transformer 308of the FIM.

In addition to the hardware disclosed above, the apparatus of thepresent disclosure includes a programming unit or a field programmablegate array (FPGA) 303, an analog multiplexer 306, an isolation unit 307,a sense resistor 309 and a sensing unit 310. The additional hardwarefunctions to identify faults in the transformer winding of the FIM. Itis thereafter, possible to switch entire control to the secondary FIM,without resulting in a live list mismatch and loss of view for thedevices 312 n connected to the FF communication links of the FIMs.

The microprocessor 301 is communicatively coupled with the FPGA 303. Themicroprocessor 301 communicates with the FPGA 303 for sending a messageto the field devices 312 n. The FPGA 303 is connected to the FFController 304. The microprocessor 301 in the normal course of operationprovides commands and instructions from the control system to the FFcontroller 304 via the FPGA 303. The FF controller 303 is alsocommunicatively connected to the MAU 305.

The transformer 308 has a transceiver side winding and a bus sidewinding. The transceiver side winding is connected to the MAU viatransceiver side winding inputs 3081 and 3082. The connection of thetransceiver side winding inputs 3081, 3082 with the MAU 305 passesthrough a summation device 311. The MAU 305 is further connected to themultiplexer 306. The multiplexer 306 is connected to the FPGA 303 and isconfigured to receive signals from the FPGA 303 as inputs. Themultiplexer 306 provides signals to the MAU 305 and to the transceiverside winding of the transformer 308. The FPGA 303 is also connected toan isolation circuit 307, for providing diagnostic signals. The output3071 and 3072 of the isolation unit 307 are connected to bus sidewinding of the transformer 308. Output 3071 of the isolation unit isconnected to bus side winding input 3083 and output 3084 of theisolation unit 307, is connected to bus side winding output 3084. Asense resistor 309 is provided in series to one end of the transceiverside winding of the transformer 308, as illustrated in FIG. 3. A sensingunit 310 is connected in parallel with the sense resistor 309. Thesensing unit 310 is connected to the FPGA 303 and provides an inputthereto. The hardware in FIG. 3, performs regular communication infieldbus communication mode. The disclosed hardware is furtherconfigured to periodically transmit a diagnostic pulse for faultdetection, according to the disclosure.

In the fieldbus communication mode, the FF controller 304 monitors theregular communication which takes place between the control system 301and the field devices 312 n and establishes a communication path betweenthe control system 301 and the field devices 312 n. The FF controller304 receives the communication from the microprocessor 302, andthereafter translates the commands and instructions for foundationfieldbus (FF) communication. In addition to the above, the FF controller304 is configured to trigger a transmitter enable signal (TXE). The FFcontroller 304 establishes the communication path by triggering the TXEsignal into an “assert” mode. The TXE signal remains in the “assert”mode until the communication between the control system 301 and fielddevices 312 n concludes. Once the communication between the controlsystem 301 and the field devices 312 n concludes, the TXE signal istriggered into a “de-assert” mode by the FF Controller 304.

When the TXE signal is triggered into the “assert” mode, the FFcontroller 304 provides the commands for field devices 312 n to the MAU305. The MAU 305 applies the commands communicated by the FF controller304, to the transformer 308. In this communication mode, signals arecommunicated to the field devices 312 n via the transformer 308. Thecurrent flow in the transformer 308, results in a voltage drop acrossthe sense resistor 309. The voltage developed across the sense resistor309 is sensed by the sensing unit 310. The sensing unit 310 amplifiesthe sensed voltage to achieve a sensed value. The sensed value isthereafter compared against a threshold value of voltage in the sensingunit 310. If the sensed value is above a threshold the channel isdeclared in good condition. The sensed voltage across the sense resistormay drop below the threshold due to an increase in impedance. Theincrease in impedance could be due to corrosion or other connectionanomaly or there may be a hardware fault in the transformer winding.

This increase in impedance results in a decrease in voltage sensed bythe sensing unit 310 across the sense resistor 309. Due to variousfactors the increase in impedance could range above 500 ohms, and as aresult the voltage across the sense resistor 309 could drop below thereference voltage of 200 mV. There are various factors which increaseimpedance, the factors include loss of power supply, open communicationlinks, termination of communication links or hardware faults within theFIM 2021.

In the field bus communication mode, if the sensed voltage is below thethreshold for a given period of time, the sensing unit 310 is configuredto trigger a “Fault” flag at the FPGA 303. As soon as the FPGA 303receives the trigger of the “Fault” flag from the sensing unit 310, theFPGA 303 starts monitoring the TXE signal generated by the FF controller304. The FPGA 303 detects the “assert” mode and “de-assert” mode of theTXE signal. When the TXE signal is in “de-assert” mode, the FPGA 303generates a diagnostics pulse (D_(P)) to determine whether the “Fault”flag was set due to real hardware fault in the transformer 308 or underthe influence of an external condition. The diagnostic pulse (D_(P)) isapplied to the multiplexer 306 and the isolation unit 307. Themultiplexer 306 interleaves the diagnostics pulse between the fieldbuscommunication signals.

The multiplexer 306 applies the diagnostic pulse (D_(P)) to thetransceiver side winding of the transformer 308, including the senseresistor 309. On the application of a current at the transceiver sidewinding of the transformer 308, the current flows through the winding.This current produces a voltage drop that is developed across the senseresistor 309. The sensing unit 310 senses the voltage drop developedacross the sense resistor 309. In case the sensing unit 310 does notsense a voltage drop across the sense resistor 309 for a predeterminedtime period, a “Fault Bit” trigger would be registered in the FPGAindicating a fault in the transformer 308. The fault thereafter iscommunicated to the control system 301 through the microprocessor 302.

The isolation unit 307 applies the diagnostic pulse (D_(P)) to the busside winding of the transformer 308. The isolation unit 307 isconfigured to short the bus side winding of the transformer 308, at theapplication of diagnostic pulse. The shorting of the bus side windinginduces a current in the transceiver side winding of the transformer308. The induced current in the transceiver side winding establishes avoltage drop across the sense resistor 309. The sensing unit 310 sensesthe voltage drop developed across the sense resistor 309. In case thesensing unit 310 does not sense a voltage drop across the sense resistor309 for a predetermined time period, a “Fault Bit” trigger would beregistered in the FPGA 303 indicating a fault in the transformer 308.The fault thereafter is communicated to the control system 301 throughthe microprocessor 302.

The diagnostics pulse, (D_(P)), disclosed above comprises a periodic Onand a periodic Off pulse. During the On pulse a current for a shortduration is transmitted through the multiplexer 306 and the isolationunit 307. Application of the On pulse effects the voltage drop at thesense resistor 309. The sensing unit 310 senses the voltage drop, andthis voltage drop is considered as a diagnostic response (DR) at thesensing unit 310. Each diagnostic response (DR) at the sensing unit 310corresponds to a voltage being sensed at the sense resistor 309. Eachdiagnostic response coincides with the On pulse, ascertaining therebythat a voltage is being sensed at the sense resistor 309. In the eventthat the diagnostic response is not received at the sensing unit 310within a predetermined time of the application of the On pulse, thenthis indicates a fault in the windings of the transformer 308, whichwould require the changeover from the primary FIM to the secondary FIM.

In an exemplary embodiment, the diagnostics pulse comprises a 40 ms Onand a 200 ms Off pulse. Each diagnostic response (DR) coincides with the40 ms On pulse, meaning that a voltage would be sensed at the senseresistor 309 for this period. In case if there is some fault in thetransformer 308, no current would be transmitted through it.Accordingly, there would not be any diagnostic response corresponding toa 40 ms On pulse. In the case, if no diagnostic response is received atthe sensing unit 310 within 1 second, this would indicate that there isa fault in the windings of the transformer 308, and a changeover fromthe primary FIM to the secondary FIM is required. The duration of the Onstate and the Off state of the diagnostics pulse, may be altered as perthe design requirement.

FIG. 4 describes an example method for detecting faults in acommunication interface, in accordance with the disclosure. At step 401the FF controller 304 is configured to generate a transmitter enablesignal TXE for the fieldbus communication mode. The TXE signal signifiesthat the FIM is being used for fieldbus communication.

Further at step 401, the FF Controller 303 establishes the communicationpath by triggering the TXE signal into an “assert” mode. The TXE signalremains in the “assert” mode till the communication between the controlsystem 301 and field devices 312 n concludes. Once the communicationbetween the control system 301 and the field devices 312 n concludes,the TXE signal is triggered into a “de-assert” mode by the FF controller303. The FPGA 303 is configured to detect the “assert” mode and“de-assert” mode of the TXE signal. Thus, the process in FIG. 4 hasstarted.

At step 402 the FPGA 303 generates a periodic diagnostic pulse. Theperiodic diagnostic pulse is generated when the TXE signal is in“de-assert” mode. The FPGA 303 generates the periodic diagnostics pulseto determine whether the “Fault” flag was set due to a hardware fault inthe transformer 308 or under influence of external conditions. In anexemplary embodiment, the diagnostics pulse may be in a 40 ms On and 200ms Off pulse. However, the duration of the On state, and the Off stateof the diagnostics pulse, may be altered as per the design requirement.

At step 403, the FPGA 303 provides the periodic diagnostics pulse to amultiplexer 306. The periodic diagnostics pulse is further applied tothe transceiver side winding of the transformer 308, by the multiplexer306. The diagnostics pulse flows through the transceiver side winding,and generates a voltage drop across the sense resistor 309.Simultaneously at step 404, the FPGA 303 provides the periodicdiagnostic pulse to an isolation unit 307. The isolation unit 307applies the periodic diagnostic pulse to the bus side winding of thetransformer 308. At the application of the diagnostic pulse to the busside winding of the transformer 308, the bus side winding becomes shortcircuited. Short circuiting the bus side winding of the transformer 308results in a complete loop for current to pass. The bus side winding ofthe transformer 308 remains shorted, during the duration of theapplication of the periodic pulse.

At this stage, a current flows in the transceiver side winding andthrough the sense resistor when both transceiver side winding and busside winding are intact and non-faulty. At step 405, the sensing unit310 senses the sense voltage. The current provides a voltage across thesense resistor 309. In case there is a fault in either the transceiverside winding or the bus side winding, no current will flow through thesense resistor 309. The sensed voltage would therefore be negligible orzero. Accordingly, at step 406 the sensed voltage is compared with areference voltage.

The comparison of the sensed voltage and the reference voltage may beperformed by a comparator housed within the sensing unit 310. Thecomparator compares two voltages and outputs a sense signal indicatingwhich is larger. At step 407, a sense signal is communicated to the FPGA303 indicating that there is no sensed voltage at the sense resistor 309for a specified time. The sense signal is received by the FPGA 303 and a“Fault bit” flag is triggered, indicating fault in the transformer 308of the FIM. At step 408, the control system, periodically check the“Fault bit” flag and initiates a changeover from the primary FIM to thesecondary FIM, or vice versa. Simultaneously, the control system breaksthe redundancy between the primary FIM and the secondary FIM and raisesan alarm to a control system operator that one of the FIMs is faulty.The control system may also raise an alarm indicating that both FIMs arefaulty and a replacement of the IOTA module is required.

With this method, it is possible to reliably detect faults in any of thetransformer windings of a FIM. This will allow to effectively isolatefault in the FIM hardware from various fault conditions on the fieldbuslink external to FIM. With the help of this disclosure, the applicationfirmware can ascertain whether there is a fault in the FIM. Knowledge offault in the FIM, lowers production cost and provides an inexpensivesolution for managing faults in an industrial control system.

SPECIFIC EMBODIMENTS

While the following is described in conjunction with specificembodiments, it will be understood that this description is intended toillustrate and not limit the scope of the preceding description and theappended claims.

A first embodiment of the disclosure is an apparatus for detectingfaults in a communication interface, the communication interfaceconnected to a field device and a device bus comprising a controllerconfigured to generate a device bus communication signal, a programmingunit communicatively connected to the controller and a controllerinterface, the programming unit configured to detect faults in thecommunication interface, and generate periodic diagnostic pulses, atransformer having a first winding connected to the controller interfaceand a second winding connected to the device bus, a multiplexerconnected to the programming unit configured to periodically apply thediagnostic pulses from the programming unit to the first winding, anisolation unit connected to the programming unit configured toperiodically apply the diagnostic pulses from the programming unit tothe second winding, a sense resistor connected in series to the firstwinding of the transformer; and a sensing unit connected to the senseresistor and the programming unit, wherein the sensing unit is arrangedto determine the voltage across the sense resistor, communicating thesensed voltage to the programming unit.

An embodiment of the disclosure is one, any or all prior embodiments inthis paragraph up through the first embodiment in this paragraph,wherein the programming unit is configured to receive the field buscommunication signal from the controller. An embodiment of thedisclosure is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph, wherein the programmingunit is configured to generate the diagnostic pulse based on the fieldbus communication signal. An embodiment of the disclosure is one, any orall of prior embodiments in this paragraph up through the firstembodiment in this paragraph, wherein the programming unit is configuredto detect a fault in the transformer based on the signal from sensingunit. An embodiment of the disclosure is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph, wherein the sensing unit comprises of an amplifier and acomparator. An embodiment of the disclosure is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph, wherein the isolation unit comprises of an optocoupler. Anembodiment of the disclosure is one, any or all of prior embodiments inthis paragraph up through the first embodiment in this paragraph,wherein the controller interface is communicatively connected to themultiplexer and the controller.

A second embodiment of the disclosure is a method for detecting faultsin a communication interface, the communication interface connected to afield device and a device bus comprising generating periodic diagnosticpulse by a programing unit, the programming unit communicativelyconnected to the controller and a controller interface, providing thediagnostic pulse to a multiplexer to periodically apply the diagnosticpulses from the programming unit to a first winding of a transformer,providing the diagnostic pulse to an isolation unit to periodically passthe diagnostic pulses from the programming unit to a second winding of atransformer; sensing a voltage drop across a sense resistor, the sensingunit having an input connected to the sense resistor and an outputconnected to the programming unit, comparing the voltage drop across thesense resistor with a reference value voltage value, communicating asense signal based on the comparison to the programming unit, andswitching from a primary or a secondary module to the other based on thesense signal.

An embodiment of the disclosure is one, any or all of prior embodimentsin this paragraph up through the second embodiment in this paragraphfurther comprises generating a field bus communication signal by thecontroller and receives the field bus communication signal at theprogramming unit. An embodiment of the disclosure is one, any or all ofprior embodiments in this paragraph up through the second embodiment inthis paragraph, wherein generating periodic diagnostic pulse comprisesgenerate the diagnostic pulse based on the field bus communicationsignal. An embodiment of the disclosure is one, any or all of priorembodiments in this paragraph up through the second embodiment in thisparagraph, wherein switching comprises detecting a fault in thetransformer based on the signal from sensing unit. An embodiment of thedisclosure is one, any or all of prior embodiments in this paragraph upthrough the second embodiment in this paragraph, wherein comparingcomprises amplifying the voltage drop across the sense resistor. Anembodiment of the disclosure is one, any or all of prior embodiments inthis paragraph up through the second embodiment in this paragraph,wherein providing the diagnostic pulse to an isolation unit comprisesshorting the second winding of the transformer by periodically passingthe diagnostic pulse to the second winding of the transformer.

A third embodiment of the disclosure is a system for detecting faults ina communication interface, the communication interface connected to afield device and a device bus comprising generate periodic diagnosticpulse by a programing unit, the programming unit communicativelyconnected to the controller and a controller interface, provide thediagnostic pulse to a multiplexer to periodically apply the diagnosticpulses from the programming unit to a first winding of a transformer;provide the diagnostic pulse to an isolation unit to periodically passthe diagnostic pulses from the programming unit to a second winding of atransformer; sense a voltage drop across a sense resistor, the sensingunit having an input connected to the sense resistor and an outputconnected to the programming unit, compare the voltage drop across thesense resistor with a reference value voltage value, communicate a sensesignal based on the comparison to the programming unit; and switch froma primary or a secondary module to the other based on the sense signal.

An embodiment of the disclosure is one, any or all of prior embodimentsin this paragraph up through the third embodiment in this paragraph,wherein the programming unit is configured to receive the field buscommunication signal from the controller. An embodiment of thedisclosure is one, any or all of prior embodiments in this paragraph upthrough the third embodiment in this paragraph, wherein the programmingunit is configured to generate the diagnostic pulse based on the fieldbus communication signal. An embodiment of the disclosure is one, any orall of prior embodiments in this paragraph up through the thirdembodiment in this paragraph, wherein the programming unit is configuredto detect a fault in the transformer based on the signal from sensingunit. An embodiment of the disclosure is one, any or all of priorembodiments in this paragraph up through the third embodiment in thisparagraph, wherein the sensing unit comprises of an amplifier and acomparator. An embodiment of the disclosure is one, any or all of priorembodiments in this paragraph up through the third embodiment in thisparagraph, wherein the isolation unit comprises of an optocoupler. Anembodiment of the disclosure is one, any or all of prior embodiments inthis paragraph up through the third embodiment in this paragraph,wherein the controller interface is communicatively connected to themultiplexer and the controller. An embodiment of the disclosure is one,any or all of prior embodiments in this paragraph up through the thirdembodiment in this paragraph, wherein the isolation unit shorts thesecond winding of the transformer by periodically passing the diagnosticpulse to the second winding of the transformer.

Without further elaboration, it is believed that using the precedingdescription that one skilled in the art can utilize the presentdisclosure to its fullest extent and easily ascertain the essentialcharacteristics of this disclosure, without departing from the spiritand scope thereof, to make various changes and modifications of thedisclosure and to adapt it to various usages and conditions. Thepreceding preferred specific embodiments are, therefore, to be construedas merely illustrative, and not limiting the remainder of the disclosurein any way whatsoever, and that it is intended to cover variousmodifications and equivalent arrangements included within the scope ofthe appended claims.

It may be advantageous to set forth definitions of certain words andphrases used throughout this patent document. The terms “application”and “program” refer to one or more computer programs, softwarecomponents, sets of instructions, procedures, functions, objects,classes, instances, related data, or a portion thereof adapted forimplementation in a suitable computer code (including source code,object code, or executable code). The terms “transmit,” “receive,” and“communicate,” as well as derivatives thereof, encompass both direct andindirect communication. The terms “include” and “comprise,” as well asderivatives thereof, mean inclusion without limitation. The term “or” isinclusive, meaning and/or.

The phrase “associated with,” as well as derivatives thereof, may meanto include, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, have a relationship to or with, or thelike. The term “controller” means any device, system, or part thereofthat controls at least one operation. A controller may be implemented inhardware or a combination of hardware and software/firmware. Thefunctionality associated with any controller may be centralized ordistributed, whether locally or remotely. The phrase “at least one of,”when used with a list of items, means that different combinations of oneor more of the listed items may be used, and only one item in the listmay be needed. For example, “at least one of: A, B, and C” includes anyof the following combinations: A, B, C, A and B, A and C, B and C, and Aand B and C.

While this disclosure has described certain embodiments and generallyassociated methods, alterations and permutations of these embodimentsand methods will be apparent to those skilled in the art. Accordingly,the above description of example embodiments does not define orconstrain this disclosure. Other changes, substitutions, and alterationsare also possible without departing from the spirit and scope of thisdisclosure, as defined by the following claims.

1. An apparatus for detecting faults in a communication interface, the communication interface connected to a field device and a device bus comprising: a) a controller configured to generate a device bus communication signal; b) a programming unit communicatively connected to the controller and a controller interface, the programming unit configured to: a. detect faults in the communication interface; and b. generate periodic diagnostic pulses; c) a transformer having a first winding connected to the controller interface and a second winding connected to the device bus; d) a multiplexer connected to the programming unit configured to periodically apply the diagnostic pulses from the programming unit to the first winding; e) an isolation unit connected to the programming unit configured to periodically apply the diagnostic pulses from the programming unit to the second winding, f) a sense resistor connected in series to the first winding of the transformer; and g) a sensing unit connected to the sense resistor and the programming unit, wherein the sensing unit is arranged to determine the voltage across the sense resistor, communicating the sensed voltage to the programming unit.
 2. The apparatus of claim 1, wherein the programming unit is configured to: receive the field bus communication signal from the controller.
 3. The apparatus of claim 1, wherein the programming unit is configured to: generate the diagnostic pulse based on the field bus communication signal. (claims 2 and 3 can be merged)
 4. The apparatus of claim 1, wherein the programming unit is configured to: detect a fault in the transformer based on the signal from sensing unit.
 5. The apparatus of claim 1, wherein the sensing unit comprises of an amplifier and a comparator.
 6. The apparatus of claim 1, wherein the isolation unit comprises of an optocoupler.
 7. The apparatus of claim 1, wherein the controller interface is communicatively connected to the multiplexer and the controller.
 8. A method for detecting faults in a communication interface, the communication interface connected to a field device and a device bus comprising: a) generating periodic diagnostic pulse by a programing unit, the programming unit communicatively connected to the controller and a controller interface, b) providing the diagnostic pulse to a multiplexer to periodically apply the diagnostic pulses from the programming unit to a first winding of a transformer; c) providing the diagnostic pulse to an isolation unit to periodically pass the diagnostic pulses from the programming unit to a second winding of a transformer; d) sensing a voltage drop across a sense resistor, the sensing unit having an input connected to the sense resistor and an output connected to the programming unit; e) comparing the voltage drop across the sense resistor with a reference value voltage value; f) communicating a sense signal based on the comparison to the programming unit; and g) switching from a primary or a secondary module to the other based on the sense signal.
 9. The method of claim 8 further comprises: generating a field bus communication signal by the controller; and receives the field bus communication signal at the programming unit.
 10. The method of claim 9, wherein generating periodic diagnostic pulse comprises: generate the diagnostic pulse based on the field bus communication signal.
 11. The method of claim 8, wherein switching comprises: detecting a fault in the transformer based on the signal from sensing unit.
 12. The method of claim 8, wherein comparing comprises: amplifying the voltage drop across the sense resistor.
 13. The method of claim 8, wherein providing the diagnostic pulse to an isolation unit comprises: shorting the second winding of the transformer by periodically passing the diagnostic pulse to the second winding of the transformer.
 14. A system for detecting faults in a communication interface, the communication interface connected to a field device and a device bus comprising: a) generate periodic diagnostic pulse by a programing unit, the programming unit communicatively connected to the controller and a controller interface, b) provide the diagnostic pulse to a multiplexer to periodically apply the diagnostic pulses from the programming unit to a first winding of a transformer; c) provide the diagnostic pulse to an isolation unit to periodically pass the diagnostic pulses from the programming unit to a second winding of a transformer; d) sense a voltage drop across a sense resistor, the sensing unit having an input connected to the sense resistor and an output connected to the programming unit; e) compare the voltage drop across the sense resistor with a reference value voltage value; f) communicate a sense signal based on the comparison to the programming unit; and g) switch from a primary or a secondary module to the other based on the sense signal.
 15. The system of claim 14, wherein the programming unit is configured to: receive the field bus communication signal from the controller and generate the diagnostic pulse based on the field bus communication signal.
 16. The system of claim 14, wherein the programming unit is configured to: detect a fault in the transformer based on the signal from sensing unit.
 17. The system of claim 14, wherein the sensing unit comprises of an amplifier and a comparator.
 18. The system of claim 14, wherein the isolation unit comprises of an optocoupler.
 19. The system of claim 14, wherein the controller interface is communicatively connected to the multiplexer and the controller.
 20. The system of claim 14, wherein the isolation unit: shorts the second winding of the transformer by periodically passing the diagnostic pulse to the second winding of the transformer. 